CALDB Public Release Notes Version 1.7 CALDB Date: 2000-11-07T17:00:00 I. CHANGES We have extended the time-dependent PCAD alignment file specifications to take care of more long-term drifts in derived source coordinates for all Chandra detectors. The internal document http://icxc.harvard.edu/po/ccb/ecr00/cxc-2000-056. SUMMARY: New alignment files have been derived to improve absolute aspect for observations taken since 01-Dec-1999. For HRC-S and HRC-I, the corrections are up to 2 arcsec and 1.5 arcsec, respectively. For ACIS, the corrections are less than 1 arcsec. With these alignments in place, the RMS aspect offset (radial) is 0.4 - 0.6 arcsec (compared to the requirement of 1.0 arcsec). The 0.4 arcsec value is for observations with ICRS or Hipparcos coordinates, and with one outlier (1.2 arcsec offset) removed. The 0.6 arcsec value includes all data used to derive the alignments (with USNO coords). pcadD1999-12-01alignN0001.fits pcadD2000-01-01alignN0001.fits pcadD2000-02-01alignN0001.fits pcadD2000-03-01alignN0001.fits pcadD2000-04-01alignN0001.fits pcadD2000-05-01alignN0001.fits pcadD2000-06-01alignN0001.fits pcadD2000-07-01alignN0001.fits pcadD2000-08-01alignN0001.fits pcadD2000-09-01alignN0001.fits pcadD2000-10-01alignN0001.fits pcadD2000-11-01alignN0001.fits The files are spaced monthly with effective (observation) dates as given in the corresponding filename. II. AFFECTS on PROCESSING: These files go into effect for OBS-DATE='1999-12-01T00:00:00', and continue to affect observations after that date through the present. All processing after the CALDB date 2000-11-07T17:00:00 will select from these new files for observations taken after OBS-DATE = '1999-12-01T00:00:00'. See your list of PCAD alignment calibration files, in the pcad*.fits output file headers to determine which file affected a given data set. Data processed before this CALDB date with OBS-DATE after 1999/12/01 will not be corrected for long-term drifts which these files address.